We heard that in areas where large quantities of water are stored behind
dams, the dams segment rivers and thus impede the movement of fish and
change the pattern of sediment deposition. Dams also allow the
regulation of river flows, and the preference is generally for moderate
flows with no floods and no low flows. Riverine ecosystems that evolved
before the dams were built and the life they sustain may be eliminated.
The most common examples are anadromous fish that can no longer navigate
the river and riverine species whose food cycle depends on the frequent
flooding of riverbanks. But dams also eliminate some of the effects of
severe droughts, so species that could not survive as well in the
natural hydrologic cycle may now prosper. New species, welcome and
unwelcome, may be introduced. Reservoirs often support popular game fish
that would not have been found in the natural river.

Drought also has
repercussions on the morphology and hydrologic function of stream
channel networks and on the chemistry and water quality of streams and
lakes. On land, it can lead to major episodes of tree mortality,
initiate outbreaks of insects and disease in forests, and limit an
ecosystem’s productivity and ability to cycle essential elements.

Witnesses noted that
environmental resources often receive inadequate attention during
drought emergencies and in drought planning, not so much because of lack
of concern but because of lack of expertise in this arena, lack of
adequate financial resources, and sometimes lack of awareness. Drought
planners may fail to determine which drought-related environmental
impacts can be tolerated and which cannot and therefore would benefit
from appropriate drought impact-reduction measures. Larger questions
also remain to be answered, including the degree to which humans should
try to eliminate the effect of drought on the environment if drought is
a natural part of the environmental cycle.

Additional concerns
center on use of water for humans and the environment, including
adequate stream flows for wildlife species, and determination of
preferences when one species competes with another for water. Some
people suggested that during drought, environmental regulations—ranging
from those concerning wildlife and wildlife habitat to those related to
safe drinking water—should be more flexible. On the other hand, we
heard that droughts are the very times when enforcement of such
regulations is essential to protect environmental resources, including
drinking water supplies, that are already stressed from factors not
related to drought. We heard too that addressing environmental concerns
in relation to drought might best be accomplished in the context of
ecosystem management and restoration and as part of planning for
watersheds or river basins because many of these concerns extend across
human-drawn boundaries and borders.

The Commission
appreciates the complexities of these issues. As the Western Water
Policy Review Advisory Commission stated in its June 1998 report,
"Today, there are a number of federal, state, tribal and local
agencies with competing interests and missions related to water, but
none with a sufficient political or legal mandate to override the
concerns of the others. This means that implementing any proposal, for
almost any Return
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